European VLBI Network - TOG Meeting, MDSCC Madrid, 30 June 2003 Station Report for Jodrell Bank & Cambridge Telescopes Alastair Gunn Paul Burgess November 2002 Session The November 2002 session involved 5 experiments at C-band on the Mk2 telescope (one of which was a joint MERLIN experiment and included the Cambridge telescope). A further 10 experiments were carried out at L-band using the Lovell telescope (2 of which included Cambridge). Finally, 3 experiments at K-band were performed using the Mk2 telescope (2 of these including Cambridge). C-band observations with the Mk2 telescope and Cambridge were successful but various problems effected the L- and K-band observations. Unfortunately, the entire L-band session was lost for the Lovell telescope. This was because the LO had been wrongly connected prior to the telescope being recommissioned following the replacement of the surface. The problem was not visible during the observations but the incorrect synthesiser frequency meant Jodrell Bank did not produce fringes at L-band at all. At K-band the Mk2 receiver appeared to have lock problems and no fringes were found at the correlator. At K-band the Cambridge antenna did not observe the NME due to a failure of the antenna control hardware but was succesful for the single user experiment at K-band using Cambridge. The total amount of allocated observing time was 256.5 hours (of which 79 hours were with the Mk2, 132.5 with the Lovell and 45 with Cambridge). For the Mk2, 23 hours (29%) and for Cambridge 4 hours (9%) were lost due to equipment failure and for the Lovell telescope the failure was a disappointing 100%. The C-band session was not adversely effected, however. February 2003 Session Due to a serious crack in the Effelsberg azimuth track most of the February 2002 session was cancelled and observations postponed until the May 2003 session. Jodrell Bank did observe 4 experiments at K-band (3 of which included Cambridge), one of which was the fringe test experiment and another the NME. The total allocated observing time was only 29 hours for the Mk2 and only 21 hours for Cambridge. The Mk2 observations were successful and produced fringes, although just over 1 hour (4%) was lost due to a PI using an incorrect channel patching in their experiment. Fringes were not found for Cambridge at K-band and this is likely due to incorrect LO inversion during the complex down-conversion across the microwave link. This meant a 100% failure for Cambridge this session. A series of tests were performed and the difficulties with the Cambridge LO set up for K-band have now been resolved. May 2003 Session The May 2003 session comprised 14 experiments at L-band using the Lovell telescope (10 of which included the Cambridge telescope), 5 experiments at C-band using the Mk2, 8 at 5cm using both the Mk2 and Cambridge telescopes and 2 experiments at K-band using both the Mk2 and Cambridge telescopes. The total allocated observing time was 143 hours for the Lovell, 192 for Cambridge and 124 for the Mk2 (totalling 459 hours). On the whole the session was very successful. For the Mk2, 2h41m were lost at C-band and 1h06m at K-band due to equipment failures (mainly due to tape vacuum problems). 8h33m of an 11-hour joint MERLIN experiment (gp036b) at L-band were lost on both the Lovell and Cambridge telescopes due to a date error in the conversion from VLBI to MERLIN schedules. This software error has now been rectified and will not occur again. 1h28m were lost on the Lovell due to equipment failures (again these were mostly vacuum problems). Also for the Lovell, one whole experiment was lost but this was because the PI had used the wrong line frequencies in the schedule. This error has been included in the percentages below. Overall, 15.0% of Lovell time, 4.4% of Cambridge time and 3.1% of Mk2 time were lost. This gives a total failure rate at the telescope of 7.5% (33h52m). Technical Developments 1. The VLBA DAR headstack failed (apparent fracture) and was replaced before the May 2003 session 2. The first of two Mark5 recorders arrived during the session, and has been set up and tested locally. A successful fringe test has been performed at 22GHz. The VLBA recorder will be replaced by the Mk5 system as soon as practically possible 3. Further control and monitor software improvements have been made. In particular, the use of ONOFF for the Mk2 and Lovell telescopes has now been successfully implemented by resolving conflicts between the FS and the local antenna control software. Good sets of calibration data were obtained during the May 2003 session and analysis is continuing. It is still not possible to measure total power through the microwave link for Cambridge, although solutions to this problem are being developed 3. A new TAC GPS receiver (12-channel) has been purchased. This should show some improvement in 1pps error (although the current system is adequate) 4. A grant application has been submitted for purchase of the remaining Mark5 recorders plus some 30 disk packs. This makes a total of 4 recorders purchased by Jodrell 5. Some upgraded RF equipment is being purchased and/or constructed to improve LO/IF integrity and backup 6. Further tests were done with JIVE using the PCEVN hardware, prior to the arrival of the Mk5 system. TABLE II 1) New receivers available: None at present, though a 5 GHz receiver may be available on the Lovell telescope by the end of the year. 2) Changes or new measurements of the SEFD (sytem noise in Jy): None, although we're working through recent calibration data at present. 3) Changes in polarization characteristics: None 4) Check and update the frequency range of each telescope at UHF band (30+ cm) (Footnote % in Table II) IMPORTANT: The UHF receiver is no longer available! 5) Check and update the frequency range at 21cm (Footnote # in Table II) Unchanged. By the way, the 18cm range is 1550-1730 MHz. 6) Plans to built new receivers? Yes, lots of them for e-MERLIN, but these are not relevant yet! TABLE III: Frequency Agility Please update the information on receiver agility considering the following points 7) Switch time between different frequencies (ie 6, 3.6 2cm) For the Lovell, switch time between receivers is 1 full day (no carousel) For the Mk2 and Cambridge, the carousel switch time is about 3 minutes. 8) Is the switching under schedule control ? Yes (except for the Lovell, which requires a man with a spanner!) 9) 18cm - 21cm Switching: Is this under schedule control ? Yes How long does the change take ? 30 seconds Are changes in the schedule (SNAP) file required at the stations ? Yes, and no. I don't usually change the SNAP file but place the relevant switching commands in the procedure file in the procedures which set the VC/BBC frequencies and declare the effective LOs - that's the logical place for them. But this is manual intervention, which is what your question is getting at... 10) 5cm: 6.0-6.7 GHz: Is it possible to change the frequency during the same experiment? Yes Is the change under schedule control ? Yes Are changes in the schedule (SNAP) file required at the stations ? See above... ------------------------------------------------------------------- MERLIN/VLBI National Facility Dr Alastair G Gunn Jodrell Bank Observatory University of Manchester Jodrell Bank Observatory _________ ____ Macclesfield /__ / __ \ / __ \ Cheshire SK11 9DL / / /_/ // / / / United Kingdom __ / / ___ \/ / / / tel: +44 (0)1477 571321 / /_/ / /__/ / /_/ / fax: +44 (0)1477 571618 \____/|_____/|____/ email: agg@jb.man.ac.uk -------------------------------------------------------------------